Thread-cutting mechanism for sewing machines



Jan. 11, 1927. V 1,613,634 A. R. WOOD THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed May 4, 1925 5 Sheets-Sheet l INVENTOR TNESggS BY I I v ATTORNEY A. R. WOOD THREAD CUTTING MECHANISM FOR SEWING MACHINES Jan. 11 1927.

Filed May 4. 1925 5 Sheets-Sheet 2 INVENTOR.

TTORNEY.

WITNES jES Jan. 11, 1927.

- A. R. WOOD THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed May 4. 1925 5 Sheets-Sheet 5 WITNESS;

ATTORNEY Jan. 11 1927.

A. R. WOOD THREAD CUTTING MECHANISM FOR SEWING MACHINES Filed May 4, 1925 5 Sheets-Sheet 4 INVENTOR ATTORNEY Jan. 11 1927. I

A. R. WOOD THREAD CUTTING MECHANISM FOR SEWING MACHINES ATTOR'NEY' E w xw iN N m $5 L 2% L- E N l f M .2 A K N R v w Q Q T 1 l l ITNES Patented 11, 1927.

UNITED STATES PATENT OFFICE.

ALFRED R. woonor narnenronr, CONNECTICUT, ASSIGNOR To run smdnn 11m FACTURINGCOMPANY, OF ELIZABETH, NEW'JERSEY, a conronn'rron or JERSEY.

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. Application filed May 4, 1925. Serial No. 27,627.

This invention relates to thread-cutting mechanisms for sewing machines and more particularly tomechanisms for severing and holding the under thread in a two-thread sewing machine.

The invention has for an object to so construct the mechanism in question as to avoid down pulls on the under thread leading to the last stitch, which pulls tend to draw or distort the work.v I

A further object of the invention is to provide an under-thread cutting andholding mechanism of simplified construction which is particularly adapted for use in machines for' sewing groups of stitches or buttonholes in thin and easily distorted material'. p

,To the attainment of the ends in View, means are provided for first gripping the under-thread below the work, thence severing the thread between the gripper and the work and thereafter moving the gripperto pull off and sup. 'ly suflicient slack'underthread to per-mitt e first needle-loop to draw the under-thread up to the work The severing means are preferably in the form of a shear, and means are preferably provided for releasing the gripped thread-end'after the initial stitches have been formed.

In the accompanying drawings, Fig. 1. is a side elevation, partly in section, of a buttonhole sewing machine embodying the invention. Fig. 2 is abottom plan view of the machine. Fig. 3 is a top plan view of the bracket-arm of the machine. Fig. 4 is a transverse vertical section through the machine on the line 4-4, Fig. 1. Fig. 5 is a bottomplan view of the thread-cutting and gripping devices in their initial position occupied during the sewing and as the machines comes to rest; the gripper'jaws being open. Fig. 6 is a similar View showing the open gripper jaws moved to embrace the under-thread and about to be-closed thereon. Fig. 7 shows the gripper j aws moved to extreme position after. gri ping and severing the under-thread, to pu 1 oil a supply of suclrthread for the starting of the next sewing operation. Fig. 8 shows the gripper jaws returned closed to initial position, the showing of the thread being omitted; such jaws being subsequently opened to release the under-thread when the initial stitches of thenext sewing operation have been formed.

Fig. 9 is a bottom plan view of the thread gripper elements only. Fig. 10 is a trans verse section through the machine bed on the hne 1010, Fig. 5. Fig. 11 is asimilar view on the line 11-11, Fig. 6. Fig. 12 is a slmilar view at a slightly later stage of the operation of the mechanism, showing the severing of the thread by the/(cutter. Fig. 13 is a similar view on the line 13-13, Fig. 7. Fig. 14. is a similar view on the line 1414, Fig. 8, with the slack under threadend shown held by the gripper. Fig. 15 is a perspective view of the longitudinal slide plate of the work-holder, and Fig.16 is a perspective view of the cross-slide plate of the w vork-holder.

For the purposes of the present disclosure the invention is describ as embodied in an automatic straightv buttonhole, sewing ma chme constructed substantially in accordance with the disclosure of the copending application of. E. B. .Allen, Serial No. 187,001,

filed July 23, 1921. This machine has the usual bed 1, standard 2, overhanging arm3 and head 4:. The stitch-forming mechanism comprises the reciprocating and laterally vibrating needle-ban 5 carrying the eyepointed needle 6. The needle-bar 5 is journaled in the swinging gate 7 whichis mounted on the pivot pins 8 and derives its vibra tory movement in any suitable manner from the main sewing shaft 9. For example, the

gate 7 may beconnected by means of the link 10 to the slotted arm 11 whichis fulhcrumed at 12 on the bracket-arm 3 and is connected bythe link 13 to thecrank-pin 14. mounted on the radially adjustable slide 15 carried by the rotary guide-head 16. on the Vertical shaft 17. The shaft 17 receives semi-rotational impulses through the train of gears 18 from. the shaft 19 which carries the star-wheel 20 with which mesh the pins 21, Fig. 3,- carried by the hub-of the bevel gear 22 mounted on the bearing pin 23 and receiving its motion from the bevel pinion 24 carried'by the sewing shaft 9. The gear 22 is driven at half the speed of the shaft 9 and the gearing 18 is of such ratio that the shaft 17 is given a semi-rotation for each impulse of the star-wheel 20 received from one of the pins 21. The needle-bards reciprocated by means of the usual crank 25 and link connection 26 with the sewing shaft 9 The under thread I) is carried by the bobbin element 27 of the usual shuttle (not shown) which is mounted in the race 28 and driven by means of the lower oscillatory shuttle-shaft 29 having the usual driving l connections with the crank 30 on the mainshaft 9; such connections including the crank-arm 31 and an intermediate rock-lever 32 and pitman 33.

The work is held by the usual work-clamp 10 comprising the longitudinal slide-plate 34 on a lateral extension 35 of which, Figs. 1 and 2, is pivotally mounted at 36 the upper clamp-lever 37 carrying the clamping foot 38. The longitudinal slide-plate is mounted 15 in the slideways 39, Figs. 15 and 16, in the cross slide-plate 40 which slides crosswise of the bed 1 in the Ways 41, Fig. 1. The longitudinal slide-plate 34 is actuated by means of the usual link 42, Fig. 2, and lever 43 having a follower 44 entering the longitudinal-feed cam-groove 45 in the feed-wheel 46. The cross-slide plate is actuated by the lever 47 which is fulcrumed at 48 on the bed 1 and has a follower 49 entering the lateral-feed 25 cam-groove 50 in the feed-wheel 46. The feed-wheel is mounted on. the vertical shaft 51 which is connected to be driven through a suitable system of reduction gears 52 from.

the shaft 19. This wheel is given one rev0- lution per buttonhole producing cycle.

The period of action of the stitch-forming mechanism is controlled by the usual stop-motion device comprising the tight and loose pulleys 53, 54, the belt-shipper 55 and '35 the tilting stop-motion lever 56 carrying the vertically movable spring-pressed stopplunger 57.

The particular machine chosen for disclosure of an embodiment of the invention is equipped with a control shaft 58 which is disposed transversely of the machine bed and is actuated from a constantly running power-driven pulley 59 through a suitable partial-rotation clutch mechanism including 45 a driven disk 60 carrying two angularly spaced radially slidable clutch-controlling dogs 61, Fig. 1. This mechanism is fully disclosed'in the Allen copending application Serial No. 487,001,] previously referred to 50 .and a detailed description thereof is not believed to be necessary to an understanding of the present improvement. It will suiiice toexplain that this shaft is antomaticallv 'ven a partial rotation'prior to the start ang of the stitch-forming mechanism, and a second partial rotation after the' stitchforming mechanism has come to rest. Ihe first partial rotation of the shaft 58 serves to close the work-clamp and start the stitchlw forming mechanism, and the second partial rotation of suchshaft is conveniently made use of to operate the buttonhole and threadcutting mechanismsand to open the workclamp.

i The present invention is particularly concerned with the under-thread cuttin and Figs. 7

holding mechanism. Referring to to 16 inclusive, it will be seen that'there is employed a primary lever 62 which is pivotally mounted at 63 on the under side of the cross slide-plate 40. This lever is formed intermediate its ends with a lengthwise extending slot 64 through which freely passes a screw 65 carriedby an actuating slide-bar 66 fitted in a slideway 67, Fig. 1, in the bed 1, beneath the cross slide-plate 40. The primary lever 62 has secured to its free end the spaced rigid and yielding members 68, 69, Fig. 10, constituting" one jaw of a threadgripper. The other jaw of the thread-gripper is constituted by a secondary lever 70.

which is pivoted at 71 on the primary lever .2 and is formed'at its free end With a vided with a stop-pin 74 to limit the open-' ing movement of the jaw 72. It will be observed that during the movement of the gripper-jaws from the full-line initial position to dotted-line extreme position, Fig. 2, they pass under the needle-slot '75 in the throat-plate 7 6 which is carried by the cross slide-plate 40, Fig. 16. During this movement, the sharpened leading edge 77, Fig. 12, of the primary lever 62 engages the sharpened edge 7 8 of -a ledger-blade 79 which is secured toa bar 80,- Figs. 10 and 16,

mounted on the cross slide-plate 40 and con-' stituting one of the ways 39 for the longitudinal slide-plate 34.

The cutterand gripper-actuating slidebar 66 is operated by means of a cam 81, Fig.

2, on the'control shaft 58. The cam 81 engages a follower 82 on the lever 83 pivoted at 84 on the under side of the bed 1 and having a forked free end 85 which embraces the vertical pin 86 depending from the slidebar 66 through a slot 87 in the bed 1. A spring 88 serves to, retain the follower 82 continuously in engagement with the cam 81.

In the initial position of the parts, Figs.

5 and 10, at the close ofa sewing operation,

the jaws 68, 72 are open. When the shaft 58 executes its partial rotation subsequent to sewing, the inclined portion 81' of the cam 81 acts on the lever 83 to shift the slide-bar 66 and carry the jaws 68, 72, across the lead 'of the under thread I which is slightly deflected by the inclined surface or leading edge89, Fig. 6, around the end of the jaw 72 and slips in between the open jaws 68, 72. as soon as the end of the jaw 72 is carried past said thread.

The secondary lever 70 carries a pin 90 lac 4 jaw 72 upon the thread 6, such closure taking subsequent to sewing.

place during the movement of the jaws between the positions shown in Figs. 11 and 12. As soon as the thread 6 is securely gripped, the .length thereof leading to the work is severed by coaction of the edges 77, 78 of the shear-blades 68, 79. The further movement of the jaws 68, 72 to the position shown in Fig. 13 pulls under-thread from the bobbin which is slackened upon the return of the gripper-jaws to initial position, Figs. 8 and 14; such return preferably occurring immediately following the pull-off stroke of the jaws 68, 7.2 and during the last stage of the partial rotation of the control shaft 58 When the next sewing operation is started, there is sufficient slack in the under thread bto permit the first needlelo0p to draw the under thread up to the work. After two or three stitches have been formed, the cam 93, Fig. 2, on the feed-wheel 46; swings the lever 94 and carries the laterally extended free end 95 thereof, Fig. 8, into engagement with the pin 96, on the lever 70, and shifts such lever to open the gripper-jaws and release the under thread. The spring 97 returns the lever 94 to inactive position after the cam 93 passes the latter. By gripping and severing the under thread I) close to the needle-hole 75, and thereafter pulling off slack under thread for the beginning of the next sewing operation, down-pulls of the under thread leading to the last stitch are avoided. Such down.- pulls on the under thread are particularly objectionable when sewing thin work as they distort and pucker the work and tend to draw it into the needel-slot in the throatplate, as well as causing holes to be cut in the work. The holding of the under-thread end at the be inning of the next sewin operation enab es the initial stitches o the buttonhole to be securelyand properly set,- which result is not secured when the underthread end is allowed'to hang loose. It veryj often happens that a loose under-thread end is not caught up by the initial needle-loop or loopscast about the bobbin. 9 I

The upper clamping-foot 38 of the machine is preferably. equipped'wit-h the'usual needle-thread cutter 98, Fig. l, which may be constructed and operated substantially in accordance with the'disclosure of said Allen copending application.

Having thus set forth the nature of invention, what I claim herein is- 1'.fThe combination with a throat-plate and stitch-forming devices including a reciprocating needle and under-thread mechanism, of means below the throat-plate for,

the

gripping theunder thread, means for severing the under-thread between the gripping means and the last stitch, and means for pulling ofl slack under-thread between the gripping means and the under-thread suply. p 2. The combination with a throat-plate and stitch-forming devices including a reciprocating needle and under-thread mechanism, of means below the throat-plate for gripping the under-thread, means for severing the underthread between the gripping means and the last stitch, and means for moving said thread ripping means after severance of the un er-thread to pull a length of; slack thread from the under-thread supply.

The combination with a throat-plate and stitch-forming devices including a reciprocating needle and under-thread mechanism, an under-thread gripper below the throat-plate, means for" closing said gripper upon the under-thread, means for severing the under-thread between said gripper and the last stitch, and means for thereafter imparting to said gripper a to-and-fro pull-off and thread-slackening motion of suflicient amplitude to provide enough slack under-thread to permit the first; to the work.

4. The combination with a throat-plate, a reciprocating needle and under-thread mechanism of a stationary 1e ger-blade below said t rot-plate and an under-thread pull-ofl'in the orm of a thread-gripper having. a cutting edge cooperating with said ledger-blade.

.5. The combination with stitch-forming devices of a thread-gripper ,having coacting needle-loop to be drawn up jaws movable side-wise across the lead of the thread, one of said jaws having an inclined surface adapted to deflect the thread around the free end of such jaw, thereby permitting the thread to enter between said jaws, and means for closing said jaws upon the thread.

6. Thread cutting and. holding mechanism for sewing machines comprising a primary pivoted lever formed, wit-ha cutting edge and "ondary lever to efiect closure of said jaws.

7 .'The.combination. with a throat-plate and stitch-forming devices including a regripping jaw, a secondary lever ful- 7 ciprocating needle, a loop-taker and a bobbin, of an under-thread gripper includin a pair of jaws movable in a plane parallel to the throat-plate and intermediate the throat-plate and the bobbin, one of said jaws having a cutting ed e, a stationary ledgerblade with which sald cutting edge cooperates'to produce a shear cut, means for clos- 1 ing said jaws on the under-thread, and means for moving said closed jaws to and beyond the ledger-blade to sever the under-thread and pull off a length of slack under-thread for the beginning of the next sewing opera- 5 tion.

8. The combination with a throat-plate and stitch-forming devices including a reciprocating needle, a l00p-taker and a bobbin, of means for gripping-the bobbinthread between the bobbin and the last 10 stitch, means for severing the gripped bobbin-thread close to the under side of the 1 Work, and means for thereafter moving said gripping means to pull off thread from the bobbin.

In testimony whereof, I have signed my name to this specification.

ALFRED R. WOOD. 

